This proposal is to request support for a Keystone Symposia meeting entitled "Telomere Biology and DNA Repair", organized by Roger R. Reddel, Michael B. Kastan and Titia de Lange, which will be held in Queensland, Australia from October 9-14, 2009. There is emerging evidence that telomere dysfunction has ramifications in a wide range of pathologies including cancer, bone marrow failure, pulmonary fibrosis and diseases of aging. Telomeric DNA poses special problems for the DNA repair machinery. The ends of telomeres need to avoid being recognized as DNA breaks and thereby avoid being subjected to DNA repair events that may lead to chromosome end-to-end fusions and result in chromosomal instability. The proteins that bind to telomeres and the higher order telomeric structures that protect the ends from repair events are of particular interest. Another special biological problem is posed by the gradual shortening of telomeres that occurs in somatic cells. Excessively short telomeres may trigger DNA damage checkpoints and be substrates for DNA repair reactions, and the similarities and differences between these processes at telomeres and elsewhere in the genome require examination. The role of DNA repair proteins that are present at normally functioning telomeres, and the possible role of telomere binding proteins elsewhere in the genome are of particular interest. This meeting will explore these and other exciting areas of convergence in the fields of telomere biology and DNA repair.